1. Field of the Invention
The present invention relates to an organic light emitting display device.
2. Description of Related Art
In recent years, various flat panel displays have been developed, which are relatively light-weight and smaller compared to cathode ray tubes. Among these flat panel display devices, organic light emitting display devices have come into the spotlight as the next-generation display device since organic light emitting display devices have excellent luminance and color purity by using organic compounds as the light emitting material.
However, in a conventional organic light emitting display device, the contrast may be compromised since external light is reflected by metallic materials such as thin film transistors, capacitors, and wires, all of which may be found in a display unit.
In order to minimize reductions in contrast caused by the reflection of external light, an expensive polarizing plate is often attached to the front of the conventional display device. However, the use of the polarizing plate results in increased manufacturing costs, and further reduces luminance or brightness since the polarizing plate also blocks some of the light emitted from a light emitting layer of each pixel.
Meanwhile, since organic light emitting display devices are thin, light-weight, and driven using low power consumption, organic light emitting display devices are also anticipated to be widely utilized in the field of portable display devices. Portable display devices are exposed to various external environments, which may affect the visibility of images. In order to reduce variations in the visibility of the images, a photosensor may be installed to detect a level of external light, whereby the detected level of external light my be used to control the luminance of the display unit.
However, while images are displayed on a screen of the portable display device, the light emitted from the display unit may be detected by the photosensor, so as to reduce the reliability of the photosensor. Thus, light emitted from the display unit may affect the accuracy of the photosensor. Also, a thin film transistor (‘TFT’) formed in a lower portion of the organic light emitting diode may further be sensitive to the light.